Seasonic power supplies come in all shapes and sizes. Why, once I saw one that even looked like a poodle, I did. But today, I'm not going to be looking at that one, with my apologies to any canines who might be reading this. Instead, I'm looking at one of their server models.

The unit in question is the SS-400H1U. As the nomenclature implies, this unit is 1U form factor to signify its compliance with 1U rack mount cases. The 1U refers to the height of the case - 1U is about 40mm high, with 2U, 3U, and so on being multiples of that number.

This unit isn't quite the highest power 1U power supply on the market, and not even the highest capacity from Seasonic, but it's no slouch either. It's hard to get a lot of juice into a case this big, and Seasonic did their best on this puppy. When you consider the fact that these things need to operate at high temperatures for months on end, they definitely had their work cut out for them.

Because this unit came with no fancy box full of marketing bullet points, I'm electing to reprint some of the info from the datasheet itself for you, where there are some things to brag about:

Forward converter circuit - means this could be very efficient

Super high efficiency and reliability for industrial level

Easy swap connector design - you can see the modular connectors in the picture above

High reliability ball bearing fan

Low ripple & noise - we'll see about that on page two

Smart & silent fan control (S2FC) - this is the same fan controller on most of Seasonic's consumer level offerings... not that most server units need to be silent

Zero minimum load on 3.3V rail

Short circuit protection on all outputs

Over voltage protection

Over power protection

Well, that's most of it. I was disappointed to find no mention of full power operating temperature, but since this is a server unit I'll do my best to heat it up in the hot box and see how it does. It is reasonable to expect full power for something like this to be achievable at fifty degrees Celsius, and I aim to see if it can do it.

Here's the exhaust end of this unit, along with a good look at the two 40mm Superred CHA3812DB-O fans. I have to say with these wee little noisemakers, it's not too likely Seasonic's fan controller is going to keep them very quiet.

And here's our label of the day. There's not too much interesting up there, as this is pretty much your standard ATX power supply in a different form factor. Combined 12V capacity is an adequate 348W, while the low 3.3V/5V combined rating makes this unit an unwise choice for old Pentium III's. Not that they're making new 5V based chips like that anymore.

But wait, there is something interesting up there after all - the 80 Plus logo. In fact, the unit is certified by them to pull in at least 80% at 20%, 50%, and 100% of full power. This is good news for a unit this size, as higher efficiency means less heat generated.

Seasonic SS-400H1U

+3.3V

+5V

+12V1

+12V2

-12V

+5VSB

20A

21A

16A

17A

0.8A

3A

Max Power

130W

348W

9.6W

15W

400W

And finally, here's the cabling. No sleeving for this puppy, but I do have a warning for you all. The power supply end of these cables uses Molex Mini-Fit Junior type connectors. The ATX cable goes into a 22 pin connector (bottom left), the 12V connectors go to a 20 pin connector (bottom right), and the peripheral connectors go to the 24 pin top connector.

As connectors go this is pretty idiot proof, but when dealing with that ATX cable, make sure you plug in the right connector. It's possible to plug the wrong end into the top connector, and you don't want to do that. So do make sure you're plugging only the 22 pin end of that cable into the appropriate connector on the PSU m'kay?

Type of connector:

Seasonic SS-400H1U

ATX connector (300mm)

24 pin

8-pin EPS12V connector (450mm)

1

4-pin ATX12V connector (450mm)

1

5.25" Drive (350mm+150mm)

2

5.25" Drive (450mm+150mm)

3

3.5" Drive connectors (+150mm)

1

SATA (450mm+150mm)

2

2 x 3 PCIe (600mm)

1

Unit Dimensions(L x W x H)

235mm x 100mm x 40mm

As you can see, the cables aren't all that long but there is enough there to be functional in the cases these are designed for, and there are enough connectors to get the job done as well. I was pleased to see the inclusion of a PCI-E 6 pin connector, even though most servers likely won't need a video card powerful enough to require one.

You may notice that I haven't detailed which 12V rail powers which connector this time. The reason for that is, this unit does not actually have dual 12V rails. It's single 12V all the way back to the secondary side Schottkys, with no OCP employed to split them. That makes things easy for testing.